Chasing plumes at the Endeavour Segment

The five major hydrothermal vents of the Endeavour Segment along the Juan de Fuca Ridge are estimated to emit the heat energy of a small nuclear power plant. From high temperature vent structures, this energy, along with mineral-rich vent fluids, is emitted chimney-like into the ocean, subsequently mixing with seawater and rising to neutral buoyancy between 150 and 300m above the seafloor. At this elevation, the hydrothermal vent plume is above the protection of the rift valley and is free to be carried away in the ambient ocean currents. In addition to anomalous chemical properties and particulates, the plume also carries planktonic residents of the deep-sea vent area. These larvae are key to the ongoing success of the existing ecosystems and their transport can facilitate the rapid colonization of newly formed venting sites. During Ocean Network Canada’s 2015 maintenance expedition at the Endeavour Segment, we surveyed the vent plume both along and across-axis using optical transmission to locate the plume. Analysis of our observations reveals that the plume is retained over the central axis of the valley, thus exhibiting favorable conditions for the promulgation of vent ecosystems. We compare this analysis with earlier surveys conducted by Ocean Networks Canada as well as historic data collected since 1986 by the Institute of Ocean Sciences to estimate the spatial variability of the plume. Using this we propose a “climatology” of plume spreading over the Endeavour Segment.